entry: Add null safety check in _elm_entry_entry_paste function.
entry: Add null safety check in _elm_entry_entry_paste function.

Summary: Add null safety check for the given text.

Reviewers: tasn, woohyun, thiepha, herdsman

Reviewed By: herdsman

Subscribers: thiepha, JackDanielZ

Differential Revision: https://phab.enlightenment.org/D2868

rvandegrift/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary,rvandegrift/elementary